Reflective eyepiece optical system and head-mounted near-to-eye display device

ABSTRACT

The present invention relates to a reflective eyepiece optical system and a head-mounted near-to-eye display apparatus. The system includes: a first lens group, and a first optical element and a second lens group for transmitting and reflecting a light from a miniature image displayer. The second lens group includes an optical reflection surface, and the optical reflection surface is an optical surface farthest from a human eye viewing side in the second lens group. The optical reflection surface is concave to a human eye viewing direction. The first optical element reflects the light refracted by the first lens group to the second lens group, and then transmits the light refracted, reflected, and refracted by the second lens group to the human eye.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to Chinese patent application No.202110879657. X, filed on Aug. 2, 2021, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of optical technology, andmore particularly, to a reflective eyepiece optical system and ahead-mounted near-to-eye display device.

BACKGROUND

With the development of electronic devices to ultra-miniaturization,head-mounted display devices and products are constantly emerging inmilitary, industrial, medical, educational, consumption and otherfields, and in a typical wearable computing architecture, a head-mounteddisplay device is a key component. The head-mounted display devicedirects the video image light emitted from a miniature image displayer(e.g., a transmissive or reflective liquid crystal displayer, an organicelectroluminescent element, or a DMD device) to the pupil of a user byoptical technology to implement virtual magnified images in the near-eyerange of the user, so as to provide the user with intuitive and visualimages, video, and text information. The eyepiece optical system is thecore of the head-mounted display device, which realizes the function ofdisplaying a miniature image in front of human eyes to form a virtualmagnified image.

The head-mounted display device develops in the direction of compactsize, light weight, convenient wearing, and load reduction. Meanwhile, alarge field-of-view angle and visual comfort experience have graduallybecome key factors to evaluate the quality of the head-mounted displaydevice. The large field-of-view angle determines a visual experienceeffect of high liveness, and high image quality and low distortiondetermine the comfort of visual experience. To meet these requirements,the eyepiece optical system should try its best to achieve such indexesas a large field-of-view angle, high image resolution, low distortion,small field curvature, and a small volume. It is a great challenge forsystem design and aberrations optimization to meet the above opticalproperties at the same time.

In Patent Document 1 (Chinese Patent Publication No. CN101915992A),Patent Document 2 (Chinese Patent Publication No. CN211698430U), PatentDocument 3 (Chinese Patent Publication No. CN106662678A), and PatentDocument 4 (Chinese Patent Publication No. CN105229514A), a reflectiveoptical system utilizing a combination of conventional optical sphericalsurfaces and even-order aspherical surfaces is provided respectively,wherein Patent Document 1 adopts a relay scheme, but this scheme adoptsa free-form surface reflection means, which greatly increases thedifficulty of realizing the entire optical system; the optical systemsin the Patent Document 2, Patent Document 3, and Patent Document 4 usereflective optical systems, but the basic optical structures varygreatly from one to another due to different application fields, such asin terms of a matching relationship between a lens face shape and a gapbetween the lenses.

Patent Document 5 (Chinese Patent Publication No. CN207081891U) andPatent Document 6 (Chinese Patent Publication No. CN108604007A) providean eyepiece optical system that adopts a reflex means, which ensureshigh-quality imaging; however, its optical structure is often limited tosingle lens reflection, thereby greatly limiting a performance ratio ofthe entire optical structure.

To sum up, the existing optical structures not only have problems suchas heavy weight, small field-of-view angle, and insufficient opticalperformance, but also have problems such as difficulty in processing andmass production due to the difficulty of implementation.

SUMMARY

The technical problem to be solved by the present invention is that theexisting optical structure has the problems of heavy weight, low imagequality, distortion, insufficient field-of-view, and difficulty in massproduction. In order to solve the above defects in the related art, areflective eyepiece optical system and a head-mounted near-to-eyedisplay device are provided.

A technical solution adopted by the present invention to solve thetechnical problem is constructing a reflective eyepiece optical system,including a first lens group, and a first optical element and a secondlens group for transmitting and reflecting a light from a miniatureimage displayer; wherein the second lens group includes an opticalreflection surface, and the optical reflection surface is an opticalsurface farthest from a human eye viewing side in the second lens group;the optical reflection surface is concave to a human eye viewingdirection; the first optical element reflects the light refracted by thefirst lens group to the second lens group, and then transmits the lightrefracted, reflected, and refracted by the second lens group to thehuman eye;

an effective focal length of the eyepiece optical system is f_(w), aneffective focal length of the first lens group is f₁, an effective focallength of the second lens group is f₂, and f_(w), f₁, f₂ satisfy thefollowing relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(w)<−0.64  (2);

the first lens group includes a first sub-lens group, a second sub-lensgroup, a third sub-lens group, and a fourth sub-lens group arrangedcoaxially and successively along an optical axis from the human eyeviewing side to the miniature image displayer side; an effective focallength of the first sub-lens group is f₁₁, and f₁₁ is a positive value;an effective focal length of the second sub-lens group is f₁₂, and f₁₂is a negative value; an effective focal length of the third sub-lensgroup is f₁₃, and f₁₃ is a positive value, and f₁₁, f₁₂, f₁₃, and f₁satisfy the following relations (3), (4), and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.019<f ₁₃ /f ₁  (5).

Further, a distance along the optical axis between the first opticalelement and the second lens group is d₁, a distance along the opticalaxis between the first optical element and the first lens group is d₂,and d₁ and d₂ satisfy the following relation (6):0.69<d ₂ /d ₁  (6).

Further, a maximum effective optical aperture of the second lens groupis φ₂, and φ₂ satisfies the following relation (7):φ₂<70 mm  (7).

Further, the first sub-lens group is composed of one lens, the firstsub-lens group includes a first lens, and the first lens is a positivelens.

Further, the first sub-lens group is composed of two lenses; the firstsub-lens group includes a first lens and a second lens arrangedcoaxially and successively along the optical axis from the human eyeviewing side to the miniature image displayer side; and the first lensand the second lens are both positive lenses.

Further, an effective focal length of the first lens is f₁₁, theeffective focal length of the first sub-lens group is f₁₁, and f₁₁₁ andf₁₁ satisfy the following relation (8):0.10<|f ₁₁₁ /f ₁₁|  (8).

Further, an optical surface of the first lens proximate to the human eyeviewing side is convex to the human eye.

Further, the second sub-lens group includes a third lens adjacent to thefirst sub-lens group; the third lens is a negative lens; an opticalsurface of the third lens proximate to the miniature image displayerside is concave to the miniature image displayer; an effective focallength of the third lens is f₁₂₁, and f₁₂₁ satisfies the followingrelation (9):f ₁₂₁<−5.38  (9).

Further, the third sub-lens group includes a fourth lens adjacent to thesecond sub-lens group; the fourth lens is a positive lens; an effectivefocal length of the fourth lens is f₁₃₁, and f₁₃₁ satisfies thefollowing relation (10):8.82<f ₁₃₁  (10).

Further, the fourth sub-lens group includes a fifth lens adjacent to thethird sub-lens group; an optical surface of the fifth lens proximate tothe miniature image displayer side is concave to the miniature imagedisplayer; an effective focal length of the fifth lens is f₁₄₁, and f₁₄₁satisfies the following relation (11):2.15<|f ₁₄₁ /f ₁₁|  (11).

Further, the effective focal length f₁₁ of the first sub-lens group, theeffective focal length f₁₂ of the second sub-lens group, the effectivefocal length f₁₃ of the third sub-lens group, and the effective focallength f₁ of the first lens group further satisfy the followingrelations (12), (13), and (14):0.67<f ₁₁ /f ₁<0.89  (12);−1.27<f ₁₂ /f ₁<−0.56  (13);0.85<f ₁₃ /f ₁<1.63  (14).

Further, the second lens group includes a sixth lens adjacent to thefirst optical element; the optical reflection surface is located on anoptical surface of the sixth lens distant from the human eye viewingside.

Further, the second lens group includes a sixth lens and a seventh lensadjacent to the first optical element; the sixth lens and the seventhlenses are arranged successively in an incident direction of an opticalaxis of the human eyes; and the optical reflection surface is located onan optical surface of the sixth lens distant from the human eye viewingside.

Further, the sixth lens and the miniature image displayer are movabletogether along the optical axis, for adjusting an equivalent visualvirtual image distance of the eyepiece optical system.

Further, an effective focal length of the optical reflection surface isf_(S2), the effective focal length of the second lens group is f₂, andf₂ and f_(S2) satisfy the following relation (15):0.46≤f _(S2) /f ₂≤1.0  (15).

Further, the first optical element is a planar transflective opticalelement, a reflectivity of the first optical element is Re₁, and Re₁satisfies the following relation (16):20%<Re₁<80%  (16).

Further, a reflectivity of the optical reflection surface is Re₂, andRe₂ satisfies the following relation (17):20%<Re₂  (17).

Further, an angle of optical axis between the first lens group and thesecond lens group is λ₁, and λ₁ satisfies the following relation (18):55°<λ₁<120°  (18).

Further, the eyepiece optical system further includes a planarreflective optical element located between the first lens group and thefirst optical element; the planar reflective optical element reflectsthe light refracted by the first lens group to the first opticalelement, the first optical element reflects the light to the second lensgroup, and then transmits the light refracted, reflected, and refractedby the second lens group to the human eye;

an included angle between the first lens group and the first opticalelement is λ₂, and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19).

Further, the first lens group includes one or more even-order asphericalface shapes; and the optical reflection surface is an even-orderaspherical face shape.

Further, the even-order aspherical face shape satisfies the followingrelation (20):

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + {\ldots.}}} & (20)\end{matrix}$

Further, the material of various lenses in the second lens group is anoptical plastic material.

The present application provides a head-mounted near-to-eye displaydevice, including a miniature image displayer, and further including thereflective eyepiece optical system according to any one of above items,wherein the eyepiece optical system is located between the human eye andthe miniature image displayer.

Further, the miniature image displayer is an organic electroluminescencedevice.

Further, the head-mounted near-to-eye display device includes twoidentical reflective eyepiece optical systems.

The present invention has following beneficial effects: the firstoptical element and the second lens group have transmission andreflection properties, and the second lens group includes a reflectionsurface. The eyepiece optical system composed of the first lens group,the second lens group, and the first optical element is used foreffectively folding an optical path, which reduces the overall size ofthe eyepiece optical system and improves the possibility of subsequentmass production. The first lens group includes a first sub-lens group, asecond sub-lens group, a third sub-lens group, and a fourth sub-lensgroup. The first sub-lens group, the second sub-lens group, and thethird sub-lens group adopt a focal length combination of positive,negative, and positive, and a focal length of the fourth sub-lengthgroup may be positive or negative. On the basis of miniaturization, costand weight reduction for the article, the aberrations of the opticalsystem are greatly eliminated, and the basic optical indicators are alsoimproved, ensuring high image quality and increasing the size of thepicture angle. Therefore, an observer can watch large images of fullframe, high definition and uniform image quality without any distortionand get visual experience of high liveness via the present invention,which is suitable for near-to-eye displays and similar devices thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate technical solutions of embodiments of the presentinvention or the prior art more clearly, the present invention will befurther illustrated below with reference to accompanying drawings andembodiments. The accompanying drawings described below are merely someembodiments of the present invention, and for those of ordinary skill inthe art, other accompanying drawings can be obtained according to theseaccompanying drawings without creative effort:

FIG. 1 is an optical path diagram of a reflective eyepiece opticalsystem according to a first embodiment of the present invention;

FIG. 2 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the first embodiment of the present invention;

FIG. 3 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the first embodiment of the presentinvention;

FIG. 3 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the first embodiment of the presentinvention;

FIG. 4 is a schematic diagram of an optical modulation transfer function(MTF) of the reflective eyepiece optical system according to the firstembodiment of the present invention;

FIG. 5 is an optical path diagram of a reflective eyepiece opticalsystem according to a second embodiment of the present invention;

FIG. 6 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the second embodiment of the present invention;

FIG. 7 a is a schematic diagram of a field curvature of a reflectiveeyepiece optical system according to the second embodiment of thepresent invention;

FIG. 7 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the second embodiment of thepresent invention;

FIG. 8 is a schematic diagram of an optical MTF of the reflectiveeyepiece optical system according to the second embodiment of thepresent invention;

FIG. 9 is an optical path diagram of a reflective eyepiece opticalsystem according to a third embodiment of the present invention;

FIG. 10 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the third embodiment of the present invention;

FIG. 11 a is a schematic diagram of a field curvature of a reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 11 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 12 is a schematic diagram of an optical MTF of the reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 13 a is a front view of an optical path of a reflective eyepieceoptical system according to a fourth embodiment of the presentinvention;

FIG. 13 b is a top view of an optical path of a reflective eyepieceoptical system according to a fourth embodiment of the presentinvention;

FIG. 14 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the fourth embodiment of the present invention;

FIG. 15 a is a schematic diagram of a field curvature of a reflectiveeyepiece optical system according to the fourth embodiment of thepresent invention;

FIG. 15 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the fourth embodiment of thepresent invention; and

FIG. 16 is a plot of an optical MTF of the reflective eyepiece opticalsystem according to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to clarify the objects, technical solutions and advantages ofthe embodiments of the present invention, the following clear andcomplete description will be made for the technical solution in theembodiments of the present invention. Apparently, the describedembodiments are just some rather than all embodiments of the presentinvention. All other embodiments obtained by one of ordinary skill inthe art without any creative effort based on the embodiments disclosedin the present invention fall into the scope of the present invention.

The present invention constructs a reflective eyepiece optical system,including a first lens group, and a first optical element and a secondlens group for transmitting and reflecting a light from a miniatureimage displayer. The second lens group includes an optical reflectionsurface, and the optical reflection surface is an optical surfacefarthest from a human eye viewing side in the second lens group. Theoptical reflection surface is concave to the human eye viewingdirection. The first optical element reflects the light refracted by thefirst lens group to the second lens group, and then transmits the lightrefracted, reflected, and refracted by the second lens group to thehuman eye.

The above light transmission path is as follows: a light generated bythe miniature image displayer is refracted by the first lens group andthen transmitted to the first optical element, and a reflection part onthe first optical element reflects the light into the second lens group.The optical reflection surface in the second lens group is arranged onan optical surface farthest from the human eye viewing side, andtherefore, the light will be refracted once in the second lens groupbefore entering the optical reflection surface. When the light reachesthe optical reflection surface, it will be reflected by the opticalreflection surface onto the first optical element. Before the lightreflected by the optical reflection surface reaches the first opticalelement, it will be refracted onto the first optical element throughanother optical surface in the second lens group, and alight-transmitting part on the first optical element will transmit thelight to the human eye.

An effective focal length of the eyepiece optical system is f_(w), aneffective focal length of the first lens group is f₁, an effective focallength of the second lens group is f₂, and f_(w), f₁, f₂ satisfy thefollowing relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(w)<−0.64  (2);

wherein, a value of f₁/f_(w) may be −100.57, −56.55, −33.351, −21.131,−10.951, −7.935, −5.815, −3.615, −1.589, −0.47, etc., and a value off₂/f_(w) may be −2.53, −2.521, −2.13, −1.99, −1.55, −1.21, −1.02, −0.98,−0.875, −0.753, −0.649, −0.64, and the like.

The first lens group includes a first sub-lens group, a second sub-lensgroup, a third sub-lens group, and a fourth sub-lens group arrangedcoaxially and successively along an optical axis from the human eyeviewing side to the miniature image displayer side; an effective focallength of the first sub-lens group is f₁₁, and f₁₁ is a positive value;an effective focal length of the second sub-lens group is f₁₂, and f₁₂is a negative value; an effective focal length of the third sub-lensgroup is f₁₃, and f₁₃ is a positive value, and f₁₁, f₁₂, f₁₃, and f₁satisfy the following relations (3), (4), and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.019<f ₁₃ /f ₁  (5);

wherein, a value of f₁₁/f₁ may be 0.19, 0.20, 0.39, 0.57, 0.77, 0.89,1.35, 3.25, 5.56, 36.1, 54.1, 87.6, and the like, a value of f₁₂/f₁ maybe −120.43, −100.47, −77.55, −51.25, −45.33, −21.78, −15.13, −10.55,−7.15, −4.14, −0.13, −0.02, −0.019, and the like, and a value of f₁₃/f₁may be 0.019, 0.20, 0.39, 1.99, 5.83, 12.13, 22.54, 35.24, 43.55, 83.59,and the like.

In the above relations (1), (2), (3), (4), and (5), value ranges off₁/f_(w), f₁₂/f₁, and f₁₃/f₁ are closely related to sensitivities of acorrection of system aberrations, a processing difficulty of opticalelements, and assembly deviations of the optical elements. The value off₁/f_(w) in the relation (1) is less than −0.47, which improves theprocessability of the optical elements in the system. The value off₂/f_(w) in the relation (2) is greater than −2.53, which improves theprocessability of the optical elements in the system, while its value isless than −0.64, so that the system aberrations can be fully corrected,thereby achieving higher quality optical effects. The value of f₁₁/f₁ inthe relation (3) is greater than 0.19, so that the system aberration canbe fully corrected, thereby achieving high quality optical effects. Thevalue of f₁₃/f₁ in the relation (5) is greater than 0.019, so that thesystem aberration can be fully corrected, thereby achieving high qualityoptical effects. The value of f₁₂/f₁ in the relation (4) is less than−0.019, which reduces the difficulty of spherical aberrations correctionand facilitates the realization of a large optical aperture.

The first lens group includes four sub-lens groups, which arerespectively the first sub-lens group, the second sub-lens group, thethird sub-lens group, and the fourth sub-lens group arranged adjacently.The first sub-lens group, the second sub-lens group, and the thirdsub-lens group adopt a focal length combination of positive, negative,and positive, and the focal length of the fourth lens group may be apositive focal length or a negative focal length, wherein, the negativelens group corrects aberrations, and the positive lens group providesfocused imaging. The respective sub-lens groups adopt a focal lengthcombination of “positive, negative, positive, and positive” or“positive, negative, positive, and negative,” the combination of thesub-lens groups is relatively complex, which can further correctaberrations, and has better processability, thereby fully correcting theaberrations of the system, and improving the optical resolution of thesystem.

More importantly, with the transmission and reflection properties of thefirst optical element and the second lens group, the second lens grouphas a reflection surface to effectively fold the optical path, whichreduces the overall size of the eyepiece optical system, and improvesthe possibility of subsequent mass production. At the same time, thesecond lens group and the focal length combination relationship betweenthe first sub-lens group, the second sub-lens group, the third sub-lensgroup, and the fourth sub-lens group are arranged to further correct theaberrations, which improves the processability. On the basis ofminiaturization, cost and weight reduction for the article, theaberrations of the optical system are greatly eliminated, and the basicoptical indicators are also improved, ensuring high image quality andincreasing the size of the picture angle. Therefore, an observer canwatch large images of full frame, high definition and uniform imagequality without any distortion and get visual experience of highliveness via the present invention, which is suitable for head-mountednear-to-eye display devices and similar devices thereof.

In the above embodiment, the first optical element may be a polarizerwith 75% transmission and 25% reflection, or 65% transmission and 35%reflection, or a transflective function.

As shown in FIG. 1 , a first optical element, a second lens group, and afirst lens group arranged along an optical axis from a human eye viewingside to a miniature image displayer are included. The optical surfacecloser to the human eye E side is marked as 1, and by analogy (2, 3, 4,5, 6 . . . respectively from left to right). The light emitted from theminiature image displayer is refracted by the first lens group, and thenreflected on the first optical element to the second lens group. Afterthe light is refracted, reflected, and refracted by the second lensgroup, the light transmitted by the second lens group is transmitted tothe human eye through the first optical element.

In a further embodiment, a distance along the optical axibetween thefirst optical element and the second lens group s is d₁, a distancealong the optical axis between the first optical element and the firstlens group is d₂, and d₁ and d₂ satisfy the following relation (6):0.69<d ₂ /d ₁  (6);

wherein, a value of d₂/d₁ may be 0.69, 0.695, 0.88, 0.98, 1.55, 2.37,3.55, 3.88, 3.99, 4.57, 4.89, 4.99, and the like.

A lower limit of d₂/d₁ in the above relation (6) is greater than 0.69,which reduces the difficulty of correcting an off-axis aberration of thesystem, and ensures that both a center field-of-view and an edgefield-of-view achieve high image quality, so that the image quality inthe full frame is uniform.

In a further embodiment, a maximum effective optical aperture of thesecond lens group is φ₂, and φ₂ satisfies the following relation (7):φ₂<70 mm  (7);

wherein, a value of φ₂ may be 70, 69, 65, 56, 52, 48, 32, 30, 28, 26,21, and the like, in mm.

In one embodiment, the first sub-lens group is composed of one lens, thefirst sub-lens group includes a first lens, and the first lens is apositive lens.

In one embodiment, the first sub-lens group is composed of two lenses;the first sub-lens group includes a first lens and a second lensarranged coaxially and successively along the optical axis from thehuman eye viewing side to the miniature image displayer side; and thefirst lens and the second lens are both positive lenses. Using thesecond lens can better correct the field curvature and astigmatism,which is beneficial to achieving a larger field-of-view and higheroptical resolution.

In a further embodiment, an effective focal length of the first lens isf₁₁₁, the effective focal length of the first sub-lens group is f₁₁, andf₁₁₁ and f₁₁ satisfy the following relation (8):0.10<|f ₁₁₁ /f ₁₁|  (8);

wherein, a value of |f₁₁₁/f₁₁| may be 0.10, 0.11, 0.22, 0.58, 1.32,1.55, 2.25, 3.57, 5.57, 8.79, 9.91, 10.11, 20.22, and the like.

The value of |f₁₁/f₁₁| in the relation (8) is greater than 0.19, so thatthe system aberration can be fully corrected, thereby achieving highquality optical effects.

In a further embodiment, an optical surface of the first lens proximateto the human eye viewing side is convex to the human eye direction. Itmay further reduce the size of the eyepiece optical system, improve theimage quality of the system, correct the distortion, and improve theaberrations such as astigmatism and field curvature of the system, whichis beneficial to the high-resolution optical effect of the eyepiecesystem with uniform image quality across the full frame.

In a further embodiment, the second sub-lens group includes a third lensadjacent to the first sub-lens group; the third lens is a negative lens;an optical surface of the third lens proximate to the miniature imagedisplayer side is concave to the miniature image displayer; an effectivefocal length of the third lens is f₁₂₁, and f₁₂₁ satisfies the followingrelation (9):f ₁₂₁<−5.38  (9);

wherein, a value of f₁₂₁ may be −5.38, −5.39, −6.72, −9.88, −21.32,−41.55, −52.25, −63.57, −75.57, −88.79, −99.91, −110.11, −220.22, andthe like.

The value of f₁₂₁ in the relation (9) is less than −5.38, so that thesystem aberration can be fully corrected, thereby achieving higherquality optical effects.

In a further embodiment, the third sub-lens group includes a fourth lensadjacent to the second sub-lens group; the fourth lens is a positivelens; an effective focal length of the fourth lens is f₁₃₁, and f₁₃₁satisfies the following relation (10):8.82<f ₁₃₁  (10);

wherein, a value of f₁₃₁ may be 8.82, 8.83, 9.72, 19.88, 21.32, 41.55,52.25, 63.57, 75.57, 88.79, 99.91, 110.11, 220.22, and the like.

The value of f₁₃₁ in the relation (10) is greater than 8.82, whichimproves the processability of the optical elements in the system.

In a further embodiment, the fourth sub-lens group includes a fifth lensadjacent to the third sub-lens group; an optical surface of the fifthlens proximate to the miniature image displayer side is concave to theminiature image displayer; an effective focal length of the fifth lensis f₁₄₁, and f₁₄₁ satisfies the following relation (11):2.15<|f ₁₄₁ /f ₁₁|  (11);

wherein, a value of |f₁₄₁/f₁₁| may be 2.15, 2.16, 5.25, 8.1, 14.14,26.53, 48.78, 100, 225, and the like. The value of |f₁₄₁/f₁₁| in therelation (11) is greater than 2.15, which improves the processability ofthe optical elements in the system.

In a further embodiment, the sixth lens and the miniature imagedisplayer are movable together along the optical axis, for adjusting anequivalent visual virtual image distance of the eyepiece optical system.

In a further embodiment, the effective focal length f₁₁ of the firstsub-lens group, the effective focal length f₁₂ of the second sub-lensgroup, the effective focal length f₁₃ of the third sub-lens group, andthe effective focal length f₁ of the first lens group further satisfythe following relations (12), (13), and (14):0.67<f ₁₁ /f ₁<0.89  (12);−1.27<f ₁₂ /f ₁<−0.56  (13);0.85<f ₁₃ /f ₁<1.63  (14).

wherein, a value of f₁₁/f₁ may be 0.67, 0.68, 0.679, 0.71, 0.735, 0.74,0.765, 0.778, 0.812, 0.855, 0.889, 0.89, and the like; a value of f₁₂/f₁may be −1.27, −1.26, −1.22, −1.18, −1.11, −1.06, −0.95, −0.75, −0.635,−0.56, and the like, and a value of f₁₃/f₁ may be 0.85, 0.869, 0.89,0.90, 0.95, 0.98, 0.997, 1.11, 1.21, 1.59, 1.629, 1.63, and the like.

By further optimizing the value ranges of the effective focal lengths ofthe first sub-lens group, the second sub-lens group, the third sub-lensgroup, and the system, the optical performance and the difficulty ofprocessing and manufacturing of the optical system are better balanced.

In one embodiment, the second lens group includes a sixth lens adjacentto the first optical element; and the optical reflection surface islocated on an optical surface of the sixth lens distant from the humaneye viewing side.

In one embodiment, the second lens group includes a sixth lens and aseventh lens adjacent to the first optical element; the sixth lens andthe seventh lens are arranged successively in an incident direction ofan optical axis of the human eyes; and the optical reflection surface islocated on an optical surface of the sixth lens distant from the humaneye viewing side.

In a further embodiment, an effective focal length of the opticalreflection surface is f_(S2), the effective focal length of the secondlens group is f₂, and f₂ and f_(S2) satisfy the following relation (15):0.46≤f _(S2) /f ₂≤1.0  (15);

wherein, a value of f_(S2)/f₂ may be 0.46, 0.465, 0.467, 0.5, 0.65,0.75, 0.87, 0.93, 0.97, 1.0, and the like.

The value of f_(S2)/f₂ in the relation (15) is greater than 0.46, sothat the system aberrations can be fully corrected, thereby achievinghigh quality optical effects, while the value thereof is less than 1.0,which improves the processability of the optical elements in the system.

In a further embodiment, the first optical element is a planartransflective optical element, a reflectivity of the first opticalelement is Re₁, and Re₁ satisfies the following relation (16):20%<Re₁<80%  (16);

wherein, a value of Re₁ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%,79%, 80%, and the like.

In a further embodiment, a reflectivity of the optical reflectionsurface is Re₂, and Re₂ satisfies the following relation (17):20%<Re₂  (17);

wherein, a value of Re₂ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%,80%, 99%, and the like.

In a further embodiment, an angle of optical axis between the first lensgroup and the second lens group is λ₁, and λ₁ satisfies the followingrelation (18):55°<λ₁<120°  (18).

wherein, a value of λ₁ may be 55°, 60°, 66°, 70°, 90°, 100°, 115°, 120°,and the like.

In a further embodiment, the eyepiece optical system further includes aplanar reflective optical element located between the first lens groupand the first optical element; the planar reflective optical elementreflects the light refracted by the first lens group to the firstoptical element, the first optical element reflects the light to thesecond lens group, and then transmits the light refracted, reflected,and refracted by the second lens group to the human eye.

An included angle between the first lens group and the first opticalelement is λ₂, and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19).

wherein, a value of λ₂ may be 60°, 74°, 80°, 90°, 100°, 130°, 140°,155°, 167°, 180°, and the like.

In a further embodiment, the first lens group includes one or moreeven-order aspherical face shapes; optical surfaces of the fourth lensare all even-order aspherical face shapes; and the optical reflectionsurface is an even-order aspherical face shape.

In the above embodiment, optical surfaces of the sixth lens and theseventh lens are both even-order aspherical face shapes.

In a further embodiment, the even-order aspherical face shape satisfiesthe following relation (20):

$\begin{matrix}{{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + \ldots}};} & (20)\end{matrix}$

wherein, z is a vector height of the optical surface, c is a curvatureat the aspherical vertex, k is an aspherical coefficient, α2, 4, 6 . . .are coefficients of various orders, and r is a distance coordinate froma point on a curved surface to an optical axis of a lens system.

The aberrations (including spherical aberration, coma, distortion, fieldcurvature, astigmatism, chromatic aberration, and other higher-orderaberrations) of the optical system are fully corrected, which isbeneficial for the eyepiece optical system, while realizing a largeangle of view and a large aperture, to further improve the image qualityof the central field-of-view and the edge field-of-view, and reduce theimage quality difference between the central field-of-view and the edgefield-of-view, thereby achieving more uniform image quality and lowdistortion in the full frame.

In a further embodiment, the material of various lenses in the secondlens group is an optical plastic material, such as E48R, EP5000, andOKP1.

Therefore, the aberrations at all levels of the eyepiece optical systemare fully corrected, and the manufacturing cost of the optical elementand the weight of the optical system are also controlled.

The principles, solutions, and display results of the above eyepieceoptical system will be further described below through more specificembodiments.

In the following examples, a diaphragm E may be the exit pupil ofimaging for the eyepiece optical system, which is a virtual light exitaperture. When the pupil of the human eye is at the diaphragm position,the best imaging effect can be observed. The spot diagram provided inthe following embodiment reflects a geometric structure of the imagingof the optical system, ignores the diffraction effect, and isrepresented by defocused spots formed by the cross-section of thefocused image plane with the specified field-of-view and the light ofthe specified wavelength, which can include multiple fields-of-view andlight of multiple wavelengths at the same time. Therefore, the qualityof the imaging quality of the optical system can be directly measured bythe density, shape, and size of the defocused spots of the spot diagram,and the chromatic aberration of the optical system can be directlymeasured by the dislocation degree of the defocused spots with differentwavelengths of the spot diagram. A smaller Root Mean Square (RMS) radiusof the spot diagram results in a higher imaging quality of the opticalsystem.

Example 1

The eyepiece design data of Example 1 is shown below in Table 1:

TABLE 1 Lens Net Curvature Thickness Refractive Abbe aperture ConeSurface radius (mm) (mm) index number (mm) coefficient DiaphragmInfinite 46 6 2 −37.38631 1 1.563885 60.791427 37.45487 3 −34.62967 −1reflection 38.85648 −7.349836 4 −37.38631 −20 37.29413 5 Infinite22.7896 reflection 43.35255 6 15.40411 4.555383 1.72 50.294444 8.7101451.668969 7 −25.51009 0.1996271 6.462837 −35.50161 8 −34.88349 3.4550971.8081 22.690566 6.009596 1.28079 9 24.42357 1.45755 4.432616 22.7701510 26.39954 6.397602 1.80166 44.282314 6.86511 8.666784 11 148.82257.958945 9.72983 49.9861 12 16.48132 1.00 1.544917 55.912405 15.02079 1314.20914 9.246457 14.93923 Image plane Infinite 19.73

FIG. 1 is an optical path diagram of an optical system according toExample 1, including a first lens group T1, and a first optical elementL1 and a second lens group T2 for transmitting and reflecting a lightfrom a miniature image displayer (IMG). The second lens group T2includes an optical reflection surface S2, and the optical reflectionsurface S2 is an optical surface farthest from a human eye viewing sidein the second lens group T2. The optical reflection surface S2 isconcave to the human eye viewing direction. The first optical element L1reflects the light refracted by the first lens group T1 to the secondlens group T2, and then transmits the light refracted, reflected, andrefracted by the second lens group T2 to the human eye EYE.

The first lens group T1 includes a first sub-lens group T11, a secondsub-lens group T12, a third sub-lens group T13, and a fourth sub-lensgroup T14. The first sub-lens group T11 is a positive lens group, thesecond sub-lens group T12 is a negative lens group, the third sub-lensgroup T13 is a positive lens group, and the fourth sub-lens group T14 isa negative lens group. The first sub-lens group T11 is composed of afirst lens T111, and the first lens T111 is a positive lens. The secondsub-lens group T12 is composed of a third lens T121, and the third lensT121 is a negative lens. The third sub-lens group T13 is composed of afourth lens T131, and the fourth lens T131 is a positive lens. Thefourth sub-lens group T14 is composed of a fifth lens T141, and thefifth lens T141 is a negative lens. The second lens group T2 is composedof a sixth lens T21, wherein, the optical reflection surface S2 islocated on an optical surface of the sixth lens T21 distant from a humaneye EYE viewing side. The optical reflection surface S2 is concave tothe human eye viewing direction.

An effective focal length f_(w) of the eyepiece optical system is −25.6,an effective focal length f₁ of the first lens group T1 is 12.36, aneffective focal length f₂ of the second lens group T2 is 16.64, and aneffective focal length f_(S2) of the optical reflection surface S2 is7.82. A distance d₁ along the optical axis between the first opticalelement L1 and the second lens group T2 is 21, and a distance d₂ alongthe optical axibetween the first optical element L1 and the first lensgroup T1 s is 22.79. An effective focal length f₁₁ of the first sub-lensgroup T11 is 9.18, an effective focal length f₁₂ of the second sub-lensgroup T12 is −5.39, an effective focal length f₁₃ of the third sub-lensgroup T13 is 8.83, and an effective focal length f₁₄ of the fourthsub-lens group T14 is −223.9. Then, f₁/f_(w) is −0.48, f₂/f_(w) is−0.65, f₁₁/f₁ is 0.74, f₁₁₁/f₁₁ is 1, f₁₂/f₁ is −0.436, f₁₃/f₁ is 0.71,f₁₂₁ is −5.39, f_(S2)/f₂ is 0.47, d₂/d₁ is 1.09, and λ₁ is 72°.

FIG. 2 , FIG. 3 a , FIG. 3 b , and FIG. 4 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 2

The eyepiece design data of Example 2 is shown below in Table 2:

TABLE 2 Lens Net Curvature Thickness Refractive Abbe aperture ConeSurface radius (mm) (mm) index number (mm) coefficient DiaphragmInfinite 48.44378 5 2 −40.2182 1.3 1.568832 56.059608 46.89 3 −46.32377−1.3 reflection 49.09013 −9.751992 4 −40.2182 −24 46.75869 5 Infinite 27reflection 24.08184 6 12.23289 1.433965 1.53116 56.043828 6.869062−1.991443 7 25.71187 0.5332631 7.230143 −20.7776 8 13.91728 2.0869891.61404 55.142852 7.719132 −2.416619 9 −17.47392 0.1539091 7.9142561.587358 10 −16.98719 2.033886 1.631919 23.416119 7.914555 −6.550927 1122.17282 2.423625 8.400702 −21.01529 12 14.93413 3.175467 1.72 50.35196310.40285 −6.879372 13 −165.6123 10.35898 11.02101 102.4362 14 12.030112.502148 1.79951 42.253294 15.95355 −2.097622 15 10.96995 4.02379916.24691 −3.871605 Image plane Infinite 16.81497

FIG. 5 is an optical path diagram of an optical system according toExample 2, including a first lens group T1, and a first optical elementL1 and a second lens group T2 for transmitting and reflecting a lightfrom a miniature image displayer (IMG). The second lens group T2includes an optical reflection surface S2, and the optical reflectionsurface S2 is an optical surface farthest from a human eye viewing sidein the second lens group T2. The optical reflection surface S2 isconcave to the human eye viewing direction. The first optical element L1reflects the light refracted by the first lens group T1 to the secondlens group T2, and then transmits the light refracted, reflected, andrefracted by the second lens group T2 to the human eye EYE.

The first lens group T1 includes a first sub-lens group T11, a secondsub-lens group T12, a third sub-lens group T13, and a fourth sub-lensgroup T14. The first sub-lens group T11 is a positive lens group, thesecond sub-lens group T12 is a negative lens group, the third sub-lensgroup T13 is a positive lens group, and the fourth sub-lens group T14 isa positive lens group. The first sub-lens group T11 is composed of afirst lens T111 and a second lens T112, and the first lens T111 and thesecond lens T112 are both positive lenses. The second sub-lens group T12is composed of a third lens T121, and the third lens T121 is a negativelens. The third sub-lens group T13 is composed of a fourth lens T131,and the fourth lens T131 is a positive lens. The fourth sub-lens groupT14 is composed of a fifth lens T141, and the fifth lens T141 is apositive lens. The second lens group T2 is composed of a sixth lens T21,wherein, the optical reflection surface S2 is located on an opticalsurface of the sixth lens T21 distant from the human eye EYE viewingside. The optical reflection surface S2 is concave to the human eyeviewing direction.

An effective focal length f_(w) of the eyepiece optical system is −16.3,an effective focal length f₁ of the first lens group T1 is 11.86, aneffective focal length f₂ of the second lens group T2 is 24.56, and aneffective focal length f_(S2) of the optical reflection surface S2 is14.76. A distance d₁ along the optical axis between the first opticalelement L1 and the second lens group T2 is 25.3, and a distance d₂ alongthe optical axis between the first optical element L1 and the first lensgroup T1 is 31.05. An effective focal length f₁₁ of the first sub-lensgroup T11 is 10.45, an effective focal length f₁₁₁ of the first lensT111 is 42.37, an effective focal length f₁₂ of the second sub-lensgroup T12 is −14.92, an effective focal length f₁₃ of the third sub-lensgroup T13 is 19.17, and an effective focal length f₁₄ of the fourthsub-lens group is 3202. Then, f₁/f_(w) is −0.73, f₂/f_(w) is −1.51,f₁₁/f₁ is 0.88, f₁₁₁/f₁₁ is 4.05, f₁₂/f₁ is −1.26, f₁₃/f₁ is 1.62, f₁₂₁is −14.92, f_(S2)/f₂ is 0.59, d₂/d₁ is 1.09, and λ₁ is 70°.

FIG. 6 , FIG. 7 a , FIG. 7 b , and FIG. 8 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 3

The eyepiece design data of Example 3 is shown below in Table 3:

TABLE 3 Lens Net Curvature Thickness Refractive Abbe aperture ConeSurface radius (mm) (mm) index number (mm) coefficient DiaphragmInfinite 46 6 2 −37.38631 1 1.563885 60.791427 37.45487 3 −34.62967 −1reflection 38.85648 −7.349836 4 −37.38631 −20 37.29413 5 Infinite22.7896 reflection 43.35255 6 15.40411 4.555383 1.72 50.294444 8.7101451.668969 7 −25.51009 0.1996271 6.462837 −35.50161 8 −34.88349 3.4550971.8081 22.690566 6.009596 1.28079 9 24.42357 1.45755 4.432616 22.7701510 26.39954 6.397602 1.80166 44.282314 6.86511 8.666784 11 148.82257.958945 9.72983 49.9861 12 16.48132 1.00 1.544917 55.912405 15.02079 1314.20914 9.246457 14.93923 Image plane Infinite 19.73

FIG. 9 is an optical path diagram of an optical system according toExample 3, including a first lens group T1, and a first optical elementL1 and a second lens group T2 for transmitting and reflecting a lightfrom a miniature image displayer (IMG). The second lens group T2includes an optical reflection surface S2, and the optical reflectionsurface S2 is an optical surface farthest from a human eye viewing sidein the second lens group T2. The optical reflection surface S2 isconcave to the human eye viewing direction. The first optical element L1reflects the light refracted by the first lens group T1 to the secondlens group T2, and then transmits the light refracted, reflected, andrefracted by the second lens group T2 to the human eye EYE.

The first lens group T1 includes a first sub-lens group T11, a secondsub-lens group T12, a third sub-lens group T13, and a fourth sub-lensgroup T14. The first sub-lens group T11 is a positive lens group, thesecond sub-lens group T12 is a negative lens group, the third sub-lensgroup T13 is a positive lens group, and the fourth sub-lens group T14 isa positive lens group. The first sub-lens group T11 is composed of afirst lens T111, and the first lens T111 is a positive lens. The secondsub-lens group T12 is composed of a third lens T121, and the third lensT121 is a negative lens. The third sub-lens group T13 is composed of afourth lens T131, and the fourth lens T131 is a positive lens. Thefourth sub-lens group T14 is composed of a fifth lens T141, and thefifth lens T141 is a positive lens. The second lens group T2 is composedof a sixth lens T21 and a seventh lens T22 arranged successively in anincident direction of the optical axis of the human eyes, wherein, theoptical reflection surface S2 is located on an optical surface of thesixth lens T21 distant from a human eye EYE viewing side. The opticalreflection surface S2 is concave to the human eye viewing direction.

An effective focal length f_(w) of the eyepiece optical system is−13.85, an effective focal length f₁ of the first lens group T1 is12.88, an effective focal length f₂ of the second lens group T2 is 19.6,and an effective focal length f_(S2) of the optical reflection surfaceS2 is 10.17. A distance d₁ along the optical axis between the firstoptical element L1 and the second lens group T2 is 25.56, and a distanced₂ along the optical axis between the first optical element L1 and thefirst lens group T1 is 17.9. An effective focal length f₁₁ of the firstsub-lens group T11 is 8.7, an effective focal length f₁₂ of the secondsub-lens group T12 is −7.3, an effective focal length f₁₁₁ of the firstlens T111 is 8.7, an effective focal length f₁₃ of the third sub-lensgroup T13 is 11.07, and an effective focal length f₁₄ of the fourthsub-lens group T14 is 27.81. Then, f₁/f_(w) is −0.93, f₂/f_(w) is −1.42,f₁₁/f₁ is 0.68 f₁₁₁/f₁₁ is 1, f₁₂/f₁ is −0.57, f₁₃/f₁ is 0.86, f₁₂₁ is−7.3, f_(S2)/f₂ is 0.52, d₂/d₁ is 0.7, and λ₁ is 65°.

FIG. 10 , FIG. 11 a , FIG. 11 b , and FIG. 12 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 4

The eyepiece design data of Example 4 is shown below in Table 4:

TABLE 4 Lens Net Curvature Thickness Refractive Abbe aperture ConeSurface radius (mm) (mm) index number (mm) coefficient DiaphragmInfinite 47 5 2 −54.43931 −24 reflection 48.95158 −14.05856 3 Infinite32.3114 reflection 59.65487 4 Infinite −10 reflection 13.32531 5−16.44166 −2.618275 1.53116 56.043828 7.833633 −1.749706 6 −32.72957−2.152342 7.364828 −34.94002 7 −16.67698 −6.506248 1.651133 55.9038058.317541 −2.015585 8 15.67356 −0.2656935 8.599111 0.8499103 9 20.37391−3.964838 1.64219 22.408848 8.492684 −3.615109 10 −29.40104 −2.295139.577369 −16.08668 11 −142.7324 −4.385973 1.72 50.351963 10.89104−4.662146 12 61.45032 −6.68695 12.29765 9.621991 13 −17.92474 −5 1.8099941.000073 16.57147 −6.966687 14 −19.54462 −6.85811 15.97538 −0.1664377Image plane Infinite 17.60037

FIG. 13 a and FIG. 13 b are a front view and a top view of the opticalpath of the eyepiece optical system according to Example 4, including afirst lens group T1, and a first optical element L1 and a second lensgroup T2 for transmitting and reflecting a light from a miniature imagedisplayer IMG, and further includes a planar reflective optical elementL3 located between the first lens group and the first optical element.The second lens group T2 includes an optical reflection surface S2, andthe optical reflection surface S2 is an optical surface farthest from ahuman eye viewing side in the second lens group T2. The opticalreflection surface S2 is concave to the human eye viewing direction. Theplanar reflective optical element L3 reflects the light refracted by thefirst lens group T1 to the first optical element L1, and the firstoptical element L1 reflects the light into the second lens group T2, andthen transmits the light refracted, reflected, and refracted by thesecond lens group T2 to the human eye EYE.

The first lens group T1 includes a first sub-lens group T11, a secondsub-lens group T12, a third sub-lens group T13, and a fourth sub-lensgroup T14. The first sub-lens group T11 is a positive lens group, thesecond sub-lens group T12 is a negative lens group, the third sub-lensgroup T13 is a positive lens group, and the fourth sub-lens group T14 isa positive lens group. The first sub-lens group T11 is composed of afirst lens T111 and a second lens T112, and the first lens T111 and thesecond lens T112 are both positive lenses. The second sub-lens group T12is composed of a third lens T121, and the third lens T121 is a negativelens. The third sub-lens group T13 is composed of a fourth lens T131,and the fourth lens T131 is a positive lens. The fourth sub-lens groupT14 is composed of a fifth lens T141, and the fifth lens T141 is apositive lens. The second lens group T2 is composed of a sixth lens T21,wherein, the optical reflection surface S2 is located on an opticalsurface of the sixth lens T21 distant from the human eye EYE viewingside. The optical reflection surface S2 is concave to the human eyeviewing direction.

An effective focal length f_(w) of the eyepiece optical system is −16.7,an effective focal length f₁ of the first lens group T1 is 16.76, and aneffective focal length f₂ of the second lens group T2 is 27.22. Adistance d₁ along the optical axis between the first optical element L1and the second lens group T2 is 24, and a distance d₂ along the opticalaxis between the first optical element L1 and the first lens group T1 is42.31, wherein, d₂ consists of d₂₁ and d₂₂. An effective focal lengthf₁₁ of the first sub-lens group T11 is 12.26, an effective focal lengthf₁₁₁ of the first lens T111 is 58.91, an effective focal length f₁₂ ofthe second sub-lens group T12 is −18.17, an effective focal length f₁₃of the third sub-lens group T13 is 60.2, and an effective focal lengthf₁₄ of the fourth sub-lens group T14 is 112.12. Then, f₁/f_(w) is−1.0f₂/f_(w) is −1.63, f₁₁/f₁ is 0.73, f₁₁₁/f₁₁ is 4.81, f₁₂/f₁ is−1.08, f₁₃/f₁ is 3.59, f₁₄/f₁ is 6.69, an effective focal length f₁₂₁ ofthe third lens T121 is −18.17, d₂/d₁ is 1.76, λ₁ is 74°, and λ₂ is 90°.

FIG. 14 , FIG. 15 a , FIG. 15 b , and FIG. 16 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

The data of the above first to fourth examples all meet parameterrequirements recorded in the Summary of the Invention, and results areshown in the following Table 5:

TABLE 5 f₁/f_(w) f₂/f_(w) f₁₁/f₁ f₁₁₁/f₁₁ f₁₂/f₁ f₁₃/f₁ Example 1 −0.48−0.65 0.74 1 −0.436 0.71 Example 2 −0.73 −1.51 0.88 4.05 −1.26 1.62Example 3 −0.93 −1.42 0.68 1 −0.57 0.86 Example 4 −1.0 −1.63 0.73 4.81−1.08 3.59

The present application provides a head-mounted near-to-eye displaydevice, including a miniature image displayer, and further including thereflective eyepiece optical system according to any one of above items,wherein, the eyepiece optical system is located between the human eyeand the miniature image displayer.

Preferably, the miniature image displayer is an organicelectroluminescence device.

Preferably, the head-mounted near-to-eye display device includes twoidentical reflective eyepiece optical systems.

To sum up, the first lens group of the reflective eyepiece opticalsystem in the above examples of the present invention includes threesub-lens groups, which are the first sub-lens group, the second sub-lensgroup, the third sub-lens group, and the fourth sub-lens group,respectively. The effective focal lengths of the first sub-lens group,the second sub-lens group, and the third sub-lens group adopt acombination of positive, negative, and positive, which fully correctsaberrations of the system and improves the optical resolution of thesystem. More importantly, with the transmission and reflectionproperties of the first optical element and the second lens group, thesecond lens group has a reflection surface, which effectively folds theoptical path, reduces the overall size of the eyepiece optical system,and improves the possibility of subsequent mass production. At the sametime, the second lens group and the focal length combinationrelationship between the first sub-lens group, the second sub-lensgroup, the third sub-lens group, and the fourth sub-lens group arearranged to further correct the aberrations, which improves theprocessability. On the basis of miniaturization, cost and weightreduction for the article, the aberrations of the optical system aregreatly eliminated, and the basic optical indicators are also improved,ensuring high image quality and increasing the size of the pictureangle. Therefore, an observer can watch large images of full frame, highdefinition and uniform image quality without any distortion and getvisual experience of high liveness via the present invention, which issuitable for head-mounted near-to-eye display devices and similardevices thereof.

It should be understood that, for one of ordinary skill in the art, theforegoing description can be modified or altered, and all suchmodifications and alterations fall into the scope of the attached claimsof the present invention.

What is claimed is:
 1. A reflective eyepiece optical system, composed ofa first lens group, and a first optical element and a second lens groupfor transmitting and reflecting a light from a miniature imagedisplayer; wherein the second lens group comprises an optical reflectionsurface, and the optical reflection surface is an optical surfacefarthest from a human eye viewing side in the second lens group; theoptical reflection surface is concave to the human eye; the firstoptical element reflects the light refracted by the first lens group tothe second lens group, and then transmits the light refracted,reflected, and refracted by the second lens group to the human eye; aneffective focal length of the eyepiece optical system is f_(w), aneffective focal length of the first lens group is f₁, an effective focallength of the second lens group is f₂, and f_(w), f₁, f₂ satisfy thefollowing relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(ww)<−0.64  (2); the first lens group comprises a firstsub-lens group, a second sub-lens group, a third sub-lens group, and afourth sub-lens group arranged coaxially and successively along anoptical axis from the human eye viewing side to the miniature imagedisplayer side; an effective focal length of the first sub-lens group isf₁₁, and f₁₁ is a positive value; an effective focal length of thesecond sub-lens group is f₁₂, and f₁₂ is a negative value; an effectivefocal length of the third sub-lens group is f₁₃, and f₁₃ is a positivevalue, and f₁₁, f₁₂, f₁₃, and f₁ satisfy the following relations (3),(4), and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.019<f ₁₃ /f ₁  (5).
 2. The reflective eyepiece optical systemaccording to claim 1, wherein a distance along the optical axis betweenan optical surface of the first optical element distant from the humaneye viewing side and the optical reflection surface of the second lensgroup is dd₁, a distance along the optical axis between the opticalsurface of the first optical element distant from the human eye viewingside and an optical surface of the first lens group closest to the humaneye viewing side is dd₂, and dd₁ and dd₂ satisfy the following relation(6):0.69<d ₂ /d ₁  (6).
 3. The reflective eyepiece optical system accordingto claim 1, wherein a maximum effective optical aperture of the secondlens group is φφ₂, and φφ₂ satisfies the following relation (7):φ₂<70 mm  (7).
 4. The reflective eyepiece optical system according toclaim 1, wherein the first sub-lens group is composed of two lenses; thefirst sub-lens group comprises a first lens and a second lens arrangedcoaxially and successively along the optical axis from the human eyeviewing side to the miniature image displayer side; and the first lensand the second lens are both positive lenses.
 5. The reflective eyepieceoptical system according to claim 1, wherein the second sub-lens groupis composed of a third lens adjacent to the first sub-lens group; thethird lens is a negative lens; an optical surface of the third lensproximate to the miniature image displayer side is concave to theminiature image displayer; an effective focal length of the third lensis f₁₂₁, and f₁₂₁ satisfies the following relation (9):f ₁₂₁<−5.38  (9).
 6. The reflective eyepiece optical system according toclaim 1, wherein the third sub-lens group is composed of a fourth lensadjacent to the second sub-lens group; the fourth lens is a positivelens; an effective focal length of the fourth lens is f₁₃₁, and f₁₃₁satisfies the following relation (10):8.82<f ₁₃₁  (10).
 7. The reflective eyepiece optical system according toclaim 1, wherein the fourth sub-lens group is composed of a fifth lensadjacent to the third sub-lens group; an optical surface of the fifthlens proximate to the miniature image displayer side is concave to theminiature image displayer; an effective focal length of the fifth lensis ff₁₄₁, and ff₁₄₁ satisfies the following relation (11):2.15<|f ₁₄₁ /f ₁₁|  (11).
 8. The reflective eyepiece optical systemaccording to claim 1, wherein the effective focal length f₁₁ of thefirst sub-lens group, the effective focal length f₁₂ of the secondsub-lens group, the effective focal length f₁₃ of the third sub-lensgroup, and the effective focal length f₁ of the first lens group furthersatisfy the following relations (12), (13), and (14):0.67<f ₁₁ /f ₁<0.89  (12);−1.27<f ₁₂ /f ₁<−0.56  (13);0.85<f ₁₃ /f ₁<1.63  (14).
 9. The reflective eyepiece optical systemaccording to claim 1, wherein the second lens group is composed of asixth lens and a seventh lens adjacent to the first optical element; thesixth lens and the seventh lenses are arranged successively in anincident direction of an optical axis of the human eyes; and the opticalreflection surface is located on an optical surface of the sixth lensdistant from the human eye viewing side.
 10. The reflective eyepieceoptical system according to claim 1, wherein an effective focal lengthof the optical reflection surface is f_(ss2), the effective focal lengthof the second lens group is f₂, and f₂ and f_(s2) satisfy the followingrelation (15):0.46≤f _(S2) /f ₂≤1.0  (15).
 11. The reflective eyepiece optical systemaccording to claim 1, wherein the first optical element is a planartransflective optical element, and a reflectivity of the first opticalelement is Re₁, and Re₁ satisfies the following relation (16):20%<Re₁<80%  (16).
 12. The reflective eyepiece optical system accordingto claim 1, wherein a reflectivity of the optical reflection surface isRe₂, and Re₂ satisfies the following relation (17):20%<Re₂  (17).
 13. The reflective eyepiece optical system according toclaim 1, wherein an angle of optical axis between the first lens groupand the second lens group is λ₁, and λ₁ satisfies the following relation(18):55°<λ₁<120°  (18).
 14. The reflective eyepiece optical system accordingto claim 1, wherein the eyepiece optical system further comprises aplanar reflective optical element located between the first lens groupand the first optical element; the planar reflective optical elementreflects the light refracted by the first lens group to the firstoptical element, the first optical element reflects the light to thesecond lens group, and then transmits the light refracted, reflected,and refracted by the second lens group to the human eye; an angle ofoptical axis between the first lens group and the first optical elementis λ₂, and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19).
 15. The reflective eyepiece optical system accordingto claim 1, wherein the first lens group comprises one or moreeven-order aspherical face shapes; and the optical reflection surface isan even-order aspherical face shape.
 16. The reflective eyepiece opticalsystem according to claim 1, wherein the first sub-lens group iscomposed of one lens, the first sub-lens group comprises a first lens,and the first lens is a positive lens.
 17. The reflective eyepieceoptical system according to claim 16, wherein an effective focal lengthof the first lens is f₁₁₁, the effective focal length of the firstsub-lens group is f₁₁, and f₁₁₁ and f₁₁ satisfy the following relation(8):0.10<|f ₁₁₁ /f ₁₁|  (8).
 18. The reflective eyepiece optical systemaccording to claim 16, wherein an optical surface of the first lensproximate to the human eye viewing side is convex to the human eye. 19.The reflective eyepiece optical system according to claim 1, wherein thesecond lens group is composed of a sixth lens adjacent to the firstoptical element; the optical reflection surface is located on an opticalsurface of the sixth lens distant from the human eye viewing side. 20.The reflective eyepiece optical system according to claim 19, whereinthe sixth lens and the miniature image displayer are movable togetheralong the optical axis, for adjusting an equivalent visual virtual imagedistance of the eyepiece optical system.